Abstract : A new concept eddy current technique has been developed to examine large diameter insulated pipes without removing the insulation, and in many cases, without securing system operation. The new concept allows the in place examination of piping systems using an encircling eddy current coil that is a proven eddy current technology. Eliminating the requirement to secure or drain the system or to remove the insulation from the pipe provides significant cost savings. The new concept also provides a significantly higher percentage of inspection volume coverage than ultrasonic techniques despite limitations of pipe brackets and other physical obstructions. The technique has been demonstrated on copper, copper nickel and limited carbon steel pipe ranging from 4 to 8 inches in diameter with insulation thicknesses from 1 to 2 inches.